Inheritance, Variation & Evolution
What's covered
Key facts
A scientific name consists of two parts: the genus and the species.
In DNA, A pairs with T and C pairs with G.
Genetic engineering does raise ethical concerns — modified genes can spread, e.g. through cross-pollination — so the claim "no ethical concerns" is false.
A carrier of a recessive disease has one disease allele but shows no symptoms (heterozygous, e.g. Ff for cystic fibrosis).
Cystic fibrosis is autosomal recessive because it is caused by a recessive allele on a non-sex chromosome (CFTR on chromosome 7).
Antibiotic resistance in bacteria is a modern example of natural selection: resistant bacteria survive antibiotic exposure and pass on the resistance gene.
Allopatric speciation involves three steps: isolation, different selection pressures, then genetic divergence.
Continuous variation shows a smooth range of values with no distinct categories — e.g. height, mass.
Linnaeus is credited with creating the binomial naming system.
Chromosomes are the structures inside the nucleus that carry the DNA molecules.
Sample questions
A taste of the 104 questions in this topic — answers marked. Sign up to practise the full set with spaced repetition.
Who proposed the five-kingdom classification system?
- •Carl Linnaeus
- •Carl Woese
- •Charles Darwin
- ✓Robert Whittaker
What is a gene?
- •A chromosome found only in body cells, never in gametes.
- ✓A section of DNA that codes for a specific protein.
- •A sequence of amino acids that forms one specific protein.
- •The complete set of DNA contained in a single cell.
What is a GM crop?
- •Crop bred over many generations
- •Crop given mineral supplements
- •Crop sprayed with growth hormone
- ✓Crop with altered DNA for improved traits
In a cross between two heterozygous tall plants (Tt × Tt), what is the expected ratio of tall to short offspring?
- •1 tall : 1 short
- •1 tall : 3 short
- ✓3 tall : 1 short
- •All tall plants
Why is cystic fibrosis autosomal recessive?
- •Autosomal recessive means dominant alleles on the sex chromosome.
- ✓Caused by a recessive allele on a non-sex chromosome.
- •It is caused by an extra chromosome rather than a faulty gene.
- •It only affects people with type A blood — carriers differ.
What is natural selection?
- •Humans artificially breed organisms to select desirable traits each generation.
- •Organisms actively choose strongest mates to give offspring those traits.
- ✓Organisms with advantageous traits survive and pass them on.
- •Random DNA mutation improves survival in every environment automatically.
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